Answer:
D: That her heart was smiling and welcoming him.
Step-by-step explanation:
Alex is very happy to have found the crow, and looking at the other options none of them convey the same emotion as the original sentence.
A makes it seem like it's a fragile and sensitive moment, stemming from sadness.
B It appears as if she couldn't care less about the bird, and would leave it behind.
C More of something you'd see in a love story between two people, resembling nervousness or being starstruck.